X forwarding is just too slow I don't want to wait >300ms or so for my input to generate a response. HTML + JS serves the same purpose as X forwarding with your application hosted on a remote box displaying in your local browser with the exception of javascript allowing small amounts of local computation to be performed when it makes sense.

X forwarding doesn't really address that problem, and anyway, it's slow and flaky enough over a gigabit LAN, let alone a typical internet connection.